1. Field of the Invention
The present invention relates to a battery condition detection apparatus capable of detecting a battery condition such as a temperature of a battery mounted on passenger vehicles and trucks.
2. Description of the Related Art
A method of detecting the temperature of a battery mounted on a vehicle using a thermistor has been known. For example, Japanese patent laid open publications No. JP 2003-185504, and No. JP 2005-146939 have disclosed such a method using a thermistor.
To detect a temperature of a battery mounted on a vehicle can avoid an accident such as occurrences of an abnormal state and a reduction of a life-time of the battery, and further estimate the engine starting condition under an ambient atmosphere of the vehicle when its temperature rapidly drops.
A temperature sensitive element such as a thermistor capable of detecting the temperature of the battery is electrically connected to an output lines or wirings. The connection part between the thermistor and the output wirings has a low reliability in electrical connection. For example, such thermistor and output wirings are electrically connected at the connection part with soldering, the reliability of the connection part is further decreased under a high temperature environment, for example, when it is disposed in an engine room of the vehicle. Further, when the temperature of the battery is detected based on a voltage of analogue data detected by the thermistor, there is a possibility of getting ignition noises and the like on the output wiring, in particular, in the engine room, and the detection accuracy is thereby decreased.
In case that the temperature sensitive element such as a thermistor is exposed outside, the cooling capability of the temperature sensitive element is varied according to air-flow blowing condition. For example, the cooling capability of the temperature sensitive element is greatly varied by external factors when the vehicle is stopped or the vehicle travels at a high speed. The accuracy of detecting the temperature of the battery mounted on the vehicle is decreased because the detection accuracy greatly varies by such external factors.